1. Field of the Invention
The present invention relates generally to the breeding of corn plants and, more particularly, to the manipulation of a genetic factor which alters leaf number and distribution to produce hybrid corn plants having enhanced yields.
Corn (Zea mays or maize) is the most extensively grown of all grain crops in the United States. Corn is a naturally cross-pollinated plant where pollen, derived from the male tassel at the top of the plant, is carried by the wind to the female silks produced on the ears of nearby plants. Such natural cross-pollination provides a continuing source of variation in genetic constitution.
It is of great agricultural and economic interest to provide new corn inbreds and hybrids which display an improvement in particular characteristics, such as disease resistance, standability, tolerance to environmental factors, and the like. Through proper breeding techniques, these characteristics can be introduced into new or existing inbred lines of maize which can then be used to produce superior hybrid corn. Hybrid corn is the predominant commercial type.
Heretofore, maize breeders have neglected the intentional manipulation of leaf number and distribution on maize plants. Although breeders have attempted to lower ear placement on maize plants to improve plant standability, the result has generally been a lowering of the physical placement of the ear rather than a change in the proportion of nodes and leaves above and below the ear.
2. Description of the Prior Art
A number of patents relate to the application of genetic principles to the improvement of corn plants. See, for example, U.S. Pat. Nos. 2,753,663; 3,594,152; and 3,710,511; each of which concern the manipulation of genetic male sterility in the production of hybrid maize. See also, U.S. Pat. No. 4,051,629 which relates to the introduction of an alien chromosome to mask the expression of undesirable recessive traits in the production of hybrid seed corn. U.S. Pat. No. 4,351,130 relates to the introduction of a recessive gene for tallness in plants, such as rice, which facilitates the production of hybrid seed. Dugan and Woodworth (1939) J.Am.Soc.Agron. 31:872-875 describe the effect of the removal of leaves from a corn plant on yield.